Flooding events are surprisingly common. There are surprising amounts of water in northern Britain at the moment (heavy and persistent rain swelling rivers)and as an example the link says the 2004 Indian Ocean tsunami killed more people in just 2 hours than the ongoing conflict in Syria has managed in 4 years. That is something to think about. Flooding events, in the present and in the past, have been severe and caused trauma and great loss of life. Take the drowning of the southern North Sea basin. Anyone living there, hunting or fishing or generally going about their business, would have been overwhelmed – catastrophically. Who can forget the TV images of the recent Japanese tsunami (as a result of an earthquake).
At www.slate.com/articles/health_and_science/science/2015/11/floods_led_to_… … perhaps not the most reliable of sources as far as history is concerned but it is true that floods have bedevilled humanity for ages, and the flood of Noah was so shocking it became ingrained in the memory of the survivors. Slate of course has its own view on what Noah's flood amounted to, when it happened, and how severe it might have been – but that is Slate being Slate. We are also told that in 1900 a hurricane hit Texas and killed 12,000 people while in 1931 the Yangtze burst its banks and 3.7 million people died – unimaginable.